1. Field of Invention
This invention relates to a method and apparatus for recovering an ink discharging condition in an ink jet recording apparatus. In particular, this invention relates to removal of unwanted air bubbles within a die reservoir and/or an ink jet channel, and also relates to maintaining the temperature of the ink jet recording apparatus within acceptable limits necessary to perform an ink jet printing or discharging operation.
2. Description of Related Art
U.S. Pat. No. 5,479,196 discloses an ink jet recording apparatus for removing air bubbles from an inkjet channel. As described in conjunction with FIGS. 4A and 4B, undesirable air bubbles are removed by utilizing film boiling or the precursor to film boiling to generate vapor bubbles which then coalesce with the offending bubble. This procedure has the disadvantage of requiring an active heating element within the die reservoir to remove air bubbles therein, which is impractical if not impossible, and in practice, it is difficult to create a series of small bubbles that coalesce. In addition, U.S. Pat. No. 5,479,196 does not teach the use of a means for regulating the temperature of the ink jet recording apparatus within acceptable limits, especially following the removal of undesirable air bubbles.
Accordingly, one aspect of the present invention is to avoid the disadvantages and shortcomings of the related art. Another object of the invention is to provide a method and apparatus in which undesirable air bubbles are removed by heating the ink in the die reservoir to increase vapor pressure of the ink to cause mass transfer of water vapor molecules across an interface between an air bubble and the ink. Another aspect of the invention relates to removal of air bubbles by enlarging them until the bubbles fill the entire die reservoir space. Subsequently, a priming vacuum applied to the channels for a short duration can be used to effectively remove the void along with air molecules within it.
Another aspect of the present invention relates to maintaining the ink jet recording apparatus within an acceptable temperature range or below a certain temperature so as to improve performance and/or reduce down time. Temperature can be maintained, for example, by providing a heat sink to the die reservoir. The heat sink may be integrally formed with the die reservoir, formed as part of the maintenance station, or formed as an integral part of the carriage which traverses a recording medium during a printing operation.
According to a first embodiment of the present invention, there is provided a method for recovering an ink discharging condition in an ink jet recording apparatus having a die reservoir and at least one ink channel in communication with the die reservoir. The method comprises heating ink in the die reservoir to increase vapor pressure of the ink to cause mass transfer of water vapor molecules across an interface between an air bubble and the ink, and removing air bubbles entrapped within the die reservoir and the ink channel.
Another aspect of the invention relates to an ink jet recording apparatus comprising a die reservoir containing ink, at least one ink channel in communication with the die reservoir and a heating element operable to heat the ink in a recording mode in which a heat-induced ink jet bubble is created to jet the ink onto a recording medium, and to heat the ink in an ink discharging condition recovery mode in which vapor pressure of the ink is increased to cause mass transfer of water vapor molecules across the interface between the ink and an air bubble remaining after the recording mode.
According to yet another preferred embodiment of the present invention, an ink jet recording apparatus comprises a die reservoir containing ink, at least one ink channel in communication with the die reservoir, a heating element operable to heat the ink in a recording mode and an ink discharging condition recovery mode, and a heat sink provided to the die reservoir to cool the die reservoir below a predetermined threshold temperature. In other preferred embodiments, the heat sink may be fixedly attached to the carriage that supports the die reservoir in the ink channel, the heat sink may be fixedly attached to a maintenance portion of the ink jet recording apparatus, and/or the heat sink may be integrally formed with the die reservoir and the ink channel.
These and other aspects and embodiments of the present invention will be described with reference to the following detailed description of preferred embodiments.